Field of the Invention
The present invention relates to electrophotographic photosensitive members, process cartridges, and electrophotographic apparatuses. The present invention particularly relates to an electrophotographic photosensitive member including an intermediate layer, and a process cartridge and an electrophotographic apparatus including such an electrophotographic photosensitive member.
Description of the Related Art
Organic electrophotographic photosensitive members have advantages over conventional inorganic electrophotographic photosensitive members on its harmlessness, readiness in production, and great freedom in functional design because of a variety of constitutional materials to be selected. Such organic electrophotographic photosensitive members have been broadly used in, the market with recent rapid spread of laser beam printers.
The organic photosensitive member often includes an intermediate layer disposed between an electroconductive support and a photosensitive layer to cover defects on the electroconductive support, give adhesiveness to the photosensitive layer, prevent interference fringes, protect electrical breakage of the photosensitive layer, and prevent injection of holes from the electroconductive support to the photosensitive layer (see Japanese Patent Application Laid-Open No. S58-95351).
The intermediate layer has such advantages while having disadvantages: For example, charges are readily accumulated in the intermediate layer. The charges accumulated in the intermediate layer significantly fluctuate potential during continuous printing, causing image deficits. For example, if an organic photosensitive member having such an intermediate layer is used in development process widely used in printers at present in which dark potential portions are non-developed portions and bright potential portions are developed portions (so-called reversal development system), the sensitivity of portions exposed to light during the previous print may be increased by a reduced bright potential or residual potential, causing a ghost phenomenon (positive ghost) to significantly appear that the previous print portions appear as black portions on a solid white image output during the next print. Conversely, the sensitivity of portions exposed to light during the previous print may be reduced by an increased bright potential, causing a so-called ghost phenomenon (negative ghost) to significantly appear that the previous print portions appear as white portions on a solid black image output during the next print.
A variety of methods for reducing a fluctuation in potential caused by an increase in residual potential or a reduction in initial potential and the like to enhance durability are proposed in continuous print using an organic photosensitive member including an intermediate layer. Unfortunately, these methods cause many problems such as a reduction in initial sensitivity or charging ability, and these problems remain unsolved yet.
A recent trend toward high-quality color images has been increasing severe requirements for the photosensitive member. A photosensitive member which does not change properties due to an environmental variation in use and does not cause a fluctuation in potential and image deterioration such as ghost when used under severe environments is desired.
As one of methods for solving these problems, a method of adding metal oxide and a monophosphine oxide compound to an intermediate layer to improve a fluctuation in potential under an environment of normal temperature and low humidity is proposed. It cannot be said yet, however, that this method provides an intermediate layer perfectly satisfying the requirements for use under severe environments of high humidity/high temperature and low humidity deteriorating the durability of the photosensitive member (see Japanese Patent Application Laid-Open No. 2012-27323).
Although examples are found in which a compound represented by the formula (1) (described later) used in the present invention is used in EL elements, use of this compound in the intermediate layer of the organic photosensitive member is not described (see Japanese Patent. Application Laid-Open No. 2007-524672).